Photometers for the measurement of the intensity of scattered light at one or more angular positions about a sample cell holding a liquid or particle suspension illuminated by a light beam are known. The sample is confined to the container, or cell, and problems of light absorption, reflection and refraction at the cell wall or various interfaces are encountered. Flow type systems also are known in which the particles are passed across a small illuminated area and scatter light is collected by a number of photodetectors positioned at different angles with respect to the illuminating beam. The signal from each photodetector is used to determine one point in the scatter intensity versus angle characteristic of the particle. A detailed scatter pattern requires many points and thus many individually calibrated detectors and signal processing channels. In alternative arrangements, a single illuminating beam and single photodetector are employed. The particle to be analyzed is stationary, and either the beam or detector acceptance geometry is rotated for measurment through a range of scatter angles. However, such arrangements involve the use of rotating parts which are subject to wear and which are difficult to maintain in proper alignment and operating condition.
It is a general object of this invention to provide an improved particle analyzing method and apparatus which overcome the above-mentioned difficulties and shortcomings of the prior art devices. A more particular object is to provide a particle analyzing method and apparatus for measuring light scattering characteristics of small particles in a flow system which is capable of operating over a wide continuous range of angles, and by means of which the identity of the particle producing the light scattering characteristic may be readily determined.